Dependence of the thickness profile of pulsed laser deposited bismuth films on process parameters

High resolution, two-dimensional thickness profiles of ArF excimer laser deposited Bi films are recorded by a microdensitometer. The azimuthal dependent cross-sectional profiles are consistently fitted by linear combinations of a cos4Θ evaporation-like component and a much more sharply peaked one with exponents ranging from 8 to 61. When keeping the laser spot dimensions fixed, no dependence on laser fluence is obtained. An increase in Ar pressure from 10-6 to 10-1 Torr leads to the sharpening of the angular distribution along both axes: the forward directed component narrows from cos23Θ to cos61Θ along the short, and from cos9Θ to cos17Θ along the long axis, respectively. Further increase in pressure results in a sudden broadening leading to circular symmetry at around 0.5 Torr. Above 10-4 Torr the deposition rate continuously decreases with increasing Ar pressure. In He atmosphere only narrowing is obtained above 10-1 Torr.
This work has been carried out in the Instituto de Optica, CSIC, Madrid, Spain. One of the authors (T.S.) would like to say thanks for a NATO fellowship.